
Hi @Mabs,
Please note that this border is actually a newly rolled-out feature that color is now displayed as an outline on the browser window.
For the workaround, you can try setting the color to no color, reboot the workspace and observe the behavior.
However, apart from the workaround, there seems to be no way yet to roll back to previous design, unless you roll back Microsoft Edge to less than 125.0.2535.51, which is not recommended for concerns of security updates.
If you do not like this new design, I strongly suggest that you send feedback on the Workspace design to the Dev Team. Thank you for your support.
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Best Regards,
Shijie Li